Kate and William have confirmed that Prince George, pictured, is due a younger brother or sister in April next year. Photograph: Getty Images

The Duke and Duchess of Cambridge are due to have their second child in April next year, Kensington Palace has said.

Kate, has been suffering from another bout of hyperemesis gravidarum, or severe vomiting, which she experienced during the early stages of her first pregnancy.

A series of engagements were cancelled after the duchess’s pregnancy was announced on 8 September but her condition is improving and she will join William in officially welcoming the president of Singapore, Tony Tan, and his wife on Tuesday, as the statesman begins a four-day state visit to the UK.

Kensington Palace said in a short statement: “Their Royal Highnesses The Duke and Duchess of Cambridge are delighted to confirm they are expecting a baby in April 2015.

“The Duchess of Cambridge continues to be affected by hyperemesis gravidarum, but her condition is steadily improving.”

Confirmation of the expected birth month suggests Kate has had her 12-week scan and seen images of the baby for the first time.

With the duchess just over 12 weeks pregnant, it is likely that the baby is due around the end of April and could possibly arrive on William and Kate’s fourth wedding anniversary on 29 April.

The prince or princess will be born as the nation gears up for the general election on 7 May. If the baby is born late, it could even arrive on election day.

There has already been speculation that the baby’s birth could coincide with the 89th birthday of its great-grandmother the Queen on 21 April. Other notable royal anniversaries in April include the 10th wedding anniversary of the Prince of Wales and the Duchess of Cornwall on 9 April.